Create persistent scratch location on ESXi host using a VMware vSphere client for using USB boot Esxi

VMware recommends that ESXi has a persistent scratch location available for storing temporary data including logs, diagnostic information, and system swap. (This is not a requirement, however.) Persistent scratch space may be provisioned on a FAT 16, VMFS, or NFS partition accessible by the ESXi host.
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1033696

Using a VMware vSphere client
http://www-01.ibm.com/support/docview.wss?uid=isg3T1013015

Configuring syslog on ESXi 5.x (2003322)

VMware vSphere ESXi 5.x hosts run a syslog service (vmsyslogd) that provides a standard mechanism for logging messages from the VMkernel and other system components. By default in ESXi, these logs are placed on a local scratch volume or a ramdisk. To preserve the logs further, ESXi can be configured to place these logs to an alternate storage location on disk, and to send the logs across the network to a syslog server.

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2003322